CN104836221B - Based on the direct-current micro-grid Secondary Control control method that line loss optimizes - Google Patents
Based on the direct-current micro-grid Secondary Control control method that line loss optimizes Download PDFInfo
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- CN104836221B CN104836221B CN201510243166.0A CN201510243166A CN104836221B CN 104836221 B CN104836221 B CN 104836221B CN 201510243166 A CN201510243166 A CN 201510243166A CN 104836221 B CN104836221 B CN 104836221B
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- line loss
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Abstract
The invention belongs to distribution network technology and Power Electronic Technique crossing domain, more particularly to a kind of direct-current micro-grid Secondary Control control method optimized based on line loss.Direct current micro-grid system is built first, and top level control center calculates direct current micro-grid system line loss power according to the sample information of each changer;Then each controllable voltage source droop control intercept common mode and differential mode regulated quantity are calculated;By the output voltage of each controllable electric power in droop control parameter regulation direct-current micro-grid, exerted oneself with controlling each power supply, so as to adjust the trend on each distribution branch road, reduce line loss.In the case where the impedance of high sensor measurement circuitry and a large amount of operation informations is independent of, the present invention realizes that the line loss to direct-current grid optimizes.Test result indicate that:Compared with current direct-current micro-grid conventional control methods, the control method can effectively reduce line loss, the concrete distribution situation decision for reducing the impedance of amplitude sight path and load.
Description
Technical field
The invention belongs to distribution network technology and Power Electronic Technique crossing domain, more particularly to a kind of optimized based on line loss
Direct-current micro-grid Secondary Control control method.
Background technology
It is different from the form of conventional electrical distribution net system single power supply, tree, there are multiple direct currents in direct-current grid
Voltage source.This causes to realize that line loss optimization is possibly realized by load disturbance in power distribution network.DC micro power grid system is near
Nian Laicai progressively rises, and the method for being optimized control currently for its line loss is also rare.In exchange microgrid, part
Research carries out progressive alternate by measurement circuitry impedance and through-put power and realizes line loss optimization, but the method is too high depends on sensing
Device precision, is difficult to realize in practice, or even is run counter to desire.
For the operation of direct-current micro-grid power supply is controlled, distributed droop control method is generally adopted at present.Some researchs are each
Propose to carry out two to the sagging parameter of changer using LF communication system on the basis of power source base layer substrate operation droop control method
Secondary regulation.Some are researched and proposed by the stable busbar voltage of Secondary Control, offset the busbar voltage fluctuation that droop control brings, but
Line impedance problems are not considered;Some researchs propose the control method that each power supply flows on the basis of line impedance is considered,
But the method does not have optimization function to line loss, or even can improve line loss.
Shown in conventional droop control such as formula (1):
U*=U0-Ik (1)
Droop control can regard system as has poor tune doing closed loop to the voltage that each power supply is exported by converters
Section.The voltage-current characteristic of its output is a straight line obliquely, seals in a size for k similar in power output end
Virtual resistance.Do so can realize the common bus operation of multiple direct voltage sources, it is to avoid backflow, realization are flowed.But this side
Method can cause the floating of DC bus-bar voltage, it is impossible to carry out precise control to the output voltage of each power supply, therefore cannot also realize
Power flowcontrol is optimized with line loss.To realize power flowcontrol, and then realize that the line loss of direct-current micro-grid optimizes, must be each in microgrid
LF communication system and top level control center are introduced between changer.Electricity is exported to each port by the realization of sharing of operation information
The Secondary Control of pressure controls which and exerts oneself, so as to control the trend of whole microgrid.Even if introducing Secondary Control, how load disturbance
System loss minimization can be realized at present still without related ends.The main purpose of Secondary Control is to stablize busbar voltage at present,
The busbar voltage skew that droop control is caused is offset, its control block diagram is as shown in Figure 1a.Some researchs are based on electric power storage in micro-capacitance sensor
Pond management purpose propose by each power supply flow for the purpose of Secondary Control method, control block diagram as shown in Figure 1 b, specifically such as formula
(2),
Formula (2) although in represented each power supply current equalizing method can realize each power supply torque equilibrium, this side of exerting oneself
Formula is obviously unfavorable for the optimization of line loss.For example, when respectively there is a power supply at a certain load two ends, and connect the line of two power supplys
When roadlock resists small one and large one.To reduce line loss, it is clear that the power supply that line impedance should be made big is exerted oneself less, another power supply
Exert oneself big.And two power supply of method injunction in formula (2) is exerted oneself identical, so inevitably enlarges line loss.
In the control of some AC networks, the method for having part to realize optimization line loss by load disturbance, but these sides
Method needs to make the difference adjacent line loss twice by the impedance of sensor measurement circuitry or by the method for line loss iteration,
These methods depend on sensor accuracy unduly, are unable to reach theoretical effect in practice.
The content of the invention
Implement the multivariable Control of changer in order to using Transient Electromagnetic principle of energy balance, the present invention proposes one kind
Based on line loss optimize direct-current micro-grid Secondary Control control method, including:
Step 1, one direct current micro-grid system of structure, the system include multiple controllable voltage sources, multiple current sources or power
Source load, a plurality of transmission line of electricity, multiple changers, low bandwidth communication system, top level control center;Wherein, top level control center
Pass sequentially through low bandwidth communication system, changer bottom control platform to be connected with each controllable voltage source, top level control center leads to
Too low bandwidth communication systems are connected with current source or power source load;Transmission line of electricity is divided into power branch and trunk transmission line of electricity,
Multiple controllable voltage sources and current source or power source load are connected to together by power branch, and each bar power supply is propped up by trunk transmission line of electricity
Road and multiple current sources or power source load are connected to together;
The operation of each changer and sample information are uploaded to top level control center by step 2, low bandwidth communication system;
Step 3, top level control center calculate direct current micro-grid system circuit and damage according to the operation information transmitted on each changer
Wasted work rate;
Step 4, top level control center set up the condition of direct current micro-grid system optimal route loss power;
The each controllable voltage source droop control intercept common mode of step 5, top level control center calculation and differential mode regulated quantity;
Regulated quantity is descended into each changer by low bandwidth communication system by step 6, top level control center, by sagging control
Parameter regulation processed come realize direct current micro-grid system Secondary Control control.
The direct current micro-grid system line loss power that calculates includes each bar power branch and each bar trunk transmission line of electricity
Loss power, total formula is:
Wherein line loss P of i-th power branchliIt is calculated as follows formula:
Wherein, PlFor direct current micro-grid system line loss power, iiFor the output current of i-th controllable voltage source, i=1,
The number of 2 ..., n, n for controllable voltage source, IijFor j-th load rating electric current on i-th controllable voltage source branch road, j=1,
2 ..., m, m are the load number on the power branch, Ri(q+1)Transmit electricity for the q+1 sections on i-th controllable voltage source branch road
Line impedance, q=1,2 ..., p, p are the transmission line of electricity segmentation number on the power branch;Iq-1For on trunk transmission line of electricity
The q-1 load rating electric current, RqFor the q section transmission line of electricity impedances on trunk transmission line of electricity;A, b, c be respectively the 1st, 2,
Load sum on 3 controllable voltage source branch roads.
The condition of the optimal route loss power sets up process to be included:
Direct current micro-grid system line loss power PlObtaining minima then needs to meet:For i1、i2,
Draw
And because
Then draw and work as PlWhen obtaining minima, there is U1=U2;Can obtain in the same manner, work as PlWhen obtaining minima, U1=U2=U3
=...=Un, wherein, Pl1、Pl2The line loss of the respectively the 1st, 2 articles of power branch, i1、i2Respectively the 1st, 2 controllable voltages
The output current in source, U1、U2The current voltage measured value of the respectively the 1st, 2 controllable voltage sources, UnFor n-th controllable voltage source
Current voltage measured value, U12For the 2nd responsible running voltage on the 1st controllable voltage source branch road.
The computing formula of the intercept common mode regulation amount is:
WhereinFor intercept common mode regulation amount, GscomCommon mode regulation device, is adjusted using PI.For direct current micro-grid system
Specified busbar voltage, uaveFor the meansigma methodss of each controllable voltage source busbar voltage, each converter voltage source droop control intercept is altogether
Mould regulated quantity is identical.
The computing formula of the intercept differential mode regulated quantity is:
Wherein GsdifFor differential mode actuator, adjusted using PI.uaveFor the meansigma methodss of each controllable voltage source busbar voltage,
uiFor i-th controllable voltage source current voltage measured value, each converter voltage source droop control intercept differential mode regulated quantity difference.
The computing formula of the changer droop control parameter regulation is:
Wherein,For the output voltage of i-th controllable voltage source, U0For droop control intercept,Adjust for intercept common mode
Section amount,For intercept differential mode regulated quantity, iiFor the output current of i-th controllable voltage source, i=1,2 ..., n, n are controllable electric
The number of potential source, k are sagging line slope, and the sagging line slope of each changer of initial setting is identical, and protects in running
Hold constant.
It is second level that the low bandwidth communication system descends into the communication frequency of each changer.
The present invention has the following advantages that:
1st, microgrid line loss reaches theoretical optimum:Calculated according to direct-current micro-grid line loss analysis is solved with optimum loss
As a result as can be seen that controlling the theoretical minimum value that each power grid voltage is capable of achieving line loss according to institute's extracting method.
2nd, high-precision sensor is not relied on:The step that the physical quantity that institute's extracting method does not have size close during realizing is subtracted each other
Suddenly, therefore the deviation that cannot ignore will not be introduced because of sensor accuracy problem.
3rd, each controller operand is little:As the identification that methods described is not related to line loss is calculated and each power supply, load
Output calculation, substantially reduce the calculation resources of each controller, be conducive to improve control frequency;
4th, reliability is high:The each changer of institute's extracting method still runs droop control, and top level control center only provides droop control
Parameter regulation amount, even if therefore communication system or top level control central fault, the power supply in whole direct-current micro-grid still operates in
Droop control state, the problems such as power supply circulation will not be caused.
Description of the drawings
Fig. 1 a are the direct-current micro-grid Secondary Control control method flow chart based on voltage stabilization.
Fig. 1 b are the direct-current micro-grid Secondary Control control method flow chart flowed based on power supply.
Fig. 2 is direct-current grid structure chart.
Fig. 3 is direct-current grid circuit theory simplification figure.
Fig. 4 is the direct-current micro-grid Secondary Control control method flow chart optimized based on line loss.
Fig. 5 is the circuit example direct-current grid structure chart that organon is adopted.
Fig. 6 a are institute's extracting method line loss with line parameter circuit value situation of change schematic diagram.
Fig. 6 b are direct-current micro-grid Secondary Control control method based on voltage stabilization with line parameter circuit value situation of change schematic diagram.
Fig. 6 c are the direct-current micro-grid Secondary Control control method flowed based on power supply with line parameter circuit value situation of change schematic diagram.
Fig. 7 a are the direct-current micro-grid Secondary Control control method and institute's extracting method line loss differential meaning based on voltage stabilization
Figure.
Fig. 7 b are the direct-current micro-grid Secondary Control control method and institute's extracting method line loss differential meaning flowed based on power supply
Figure.
Specific embodiment
Build a direct current micro-grid system, as shown in Fig. 2 the system include multiple controllable voltage sources, multiple current sources or
Power source load, a plurality of transmission line of electricity, multiple changers, low bandwidth communication system, top level control center;Wherein, top level control
Center is passed sequentially through low bandwidth communication system, changer bottom control platform and is connected with each controllable voltage source, in top level control
The heart is connected with current source or power source load by low bandwidth communication system;Transmission line of electricity is divided into power branch and trunk power transmission line
Multiple controllable voltage sources and current source or power source load are connected to together by road, power branch, and trunk transmission line of electricity is electric by each bar
Source branch road and multiple current sources or power source load are connected to together;Its simplification figure is as shown in Figure 3.
In specific implementation process, it is to reduce Financial cost, low bandwidth communication system recommendations adopt bus form, such as 485,
CAN etc..Communication protocol suggestion participates in upper strata poll, the communication mode of bottom response.Due to by the way of poll one by one, if
Each changer returns the operation information of polled time, then in a communication cycle, each conversion that top level control center obtains
Device information is actually not synchronization.This will produce considerable influence to institute's extracting method.Therefore deposited using each changer simultaneously
Accumulating row information, then the communication mode for uploading one by one.It is embodied as flow process as follows:
After the completion of the q-1 time communication cycle, each changer is to be connected to the latch of top level control center the q time operation information
Before order, droop control is carried out to changer output according to the control instruction that q-1 control centres pass down, such as formula (1):
A certain moment, each changer are connected to the latches command that top level control center sends simultaneously, and now all changers are same
Shi Suocun operation information output voltage u1q、u2q、…、unqWith output current i1q、i2q、…、inq
Top level control center is polled to each changer, is returned its latch by the changer i of inquiry operation information of calling the roll
Information uiqAnd iiq
Top level control center carries out the q time droop control according to the operation information of feedback after the complete all changers of poll
The calculating of regulated quantity, specifically such as formula (2):
Top level control center is by the q time droop control regulated quantity for having calculatedWithEach conversion is sent to successively
Device, changer are only preserved after receiving the q time droop control regulated quantity, are not adjusted at once;
After top level control center has passed all changer kth time droop control regulated quantity under, synchronized update order is sent,
All changers are unified in synchronization and update droop control regulated quantity after receiving more newer commandWithThen weigh
Multiple this process.
According to above-mentioned input active power controller amount calculation procedure, the direct-current micro-grid Secondary Control optimized based on line loss is built
Control is as shown in Figure 4.
Fig. 5 is the circuit example that organon is adopted.Wherein each parameter is as shown in table 1.
1 example circuit parameter of table is chosen
Fig. 6 a-c and Fig. 7 a-b is droop control, sharing control is compared with institute extracting method line loss.Wherein Fig. 6 a-c are
The line loss of three kinds of methods is with line impedance and the situation of change of load.It is not difficult to find out that institute's extracting method can be obviously reduced
Line impedance.Line loss and institute extracting method line impedance difference of Fig. 7 a-b for other two methods in the case of same parameter.Can be with
Find out, institute's extracting method line loss is always less than other two kinds line losses, even can optimize loss 50% under certain situation
Left and right.
The above, the only present invention preferably specific embodiment, but protection scope of the present invention is not limited thereto,
Any those familiar with the art the invention discloses technical scope in, the change or replacement that can be readily occurred in,
Should all be included within the scope of the present invention.Therefore, protection scope of the present invention should be with scope of the claims
It is defined.
Claims (2)
1. it is a kind of based on line loss optimize direct-current micro-grid Secondary Control control method, it is characterised in that include:
Step 1, one direct current micro-grid system of structure, the system include that multiple controllable voltage sources, multiple current sources or power source are born
Load, a plurality of transmission line of electricity, multiple changers, low bandwidth communication system, top level control center;Wherein, top level control center is successively
It is connected with each controllable voltage source by low bandwidth communication system, changer bottom control platform, top level control is centrally through low
Bandwidth communication systems are connected with current source or power source load;Transmission line of electricity is divided into power branch and trunk transmission line of electricity, power supply
Multiple controllable voltage sources and current source or power source load are connected to together by branch road, trunk transmission line of electricity by each bar power branch with
And multiple current sources or power source load are connected to together;
The operation of each changer and sample information are uploaded to top level control center by step 2, low bandwidth communication system;
Step 3, top level control center calculate direct current micro-grid system line loss work(according to the operation information transmitted on each changer
Rate;
Step 4, top level control center set up the condition of direct current micro-grid system optimal route loss power;
The each controllable voltage source droop control intercept common mode of step 5, top level control center calculation and differential mode regulated quantity;
Regulated quantity is descended into each changer by low bandwidth communication system by step 6, top level control center, is joined by droop control
Count regulation to realize the control of direct current micro-grid system Secondary Control;
The direct current micro-grid system line loss power that calculates includes the loss of each bar power branch and each bar trunk transmission line of electricity
Power, total formula is:
Wherein line loss P of i-th power branchliIt is calculated as follows formula:
Wherein, PlFor direct current micro-grid system line loss power, iiFor the output current of i-th controllable voltage source, i=1,2 ...,
The number of n, n for controllable voltage source, IijFor j-th load rating electric current on i-th controllable voltage source branch road, j=1,2 ...,
M, m are the load number on the power branch, Ri(q+1)For the q+1 section power transmission line roadlocks on i-th controllable voltage source branch road
Anti-, q=1,2 ..., p, p are the transmission line of electricity segmentation number on the power branch;Iq-1For the q-1 on trunk transmission line of electricity
Individual load rating electric current, RqFor the q section transmission line of electricity impedances on trunk transmission line of electricity;A, b, c respectively the 1st, 2,3 is controllable
Load sum on voltage source branch road;
The condition of the optimal route loss power sets up process to be included:
Direct current micro-grid system line loss power PlObtaining minima then needs to meet:For i1、i2,
Draw
And because
Then draw and work as PlWhen obtaining minima, there is U1=U2;Can obtain in the same manner, work as PlWhen obtaining minima, U1=U2=U3=...=
Un, wherein, Pl1、Pl2The line loss of the respectively the 1st, 2 articles of power branch, i1、i2Respectively the 1st, 2 controllable voltage sources it is defeated
Go out electric current, U1、U2The current voltage measured value of the respectively the 1st, 2 controllable voltage sources, UnFor the current of n-th controllable voltage source
Voltage measuring value, U12For the running voltage of the 2nd load on the 1st controllable voltage source branch road;
The computing formula of the intercept common mode regulation amount is:
WhereinFor intercept common mode regulation amount, GscomFor common mode regulation device, adjusted using PI,For direct current micro-grid system volume
Determine busbar voltage, uaveFor the meansigma methodss of each controllable voltage source busbar voltage, each converter voltage source droop control intercept common mode
Regulated quantity is identical;
The computing formula of the intercept differential mode regulated quantity is:
Wherein GsdifDifferential mode actuator, is adjusted using PI, uaveFor the meansigma methodss of each controllable voltage source busbar voltage, uiFor i-th
Individual controllable voltage source current voltage measured value, each converter voltage source droop control intercept differential mode regulated quantity are different;
The computing formula of the changer droop control parameter regulation is:
Wherein,For the output voltage of i-th controllable voltage source, U0For droop control intercept,For intercept common mode regulation amount,For intercept differential mode regulated quantity, iiFor the output current of i-th controllable voltage source, i=1,2 ..., n, n are controllable voltage source
Number, k are sagging line slope, and the sagging line slope of each changer of initial setting is identical, and keeps in running constant.
2. method according to claim 1, it is characterised in that the low bandwidth communication system descends into the communication of each changer
Frequency is second level.
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